Turbocharger control

ABSTRACT

A CONTROL UNIT WHICH IS PARTICULARLY USEFUL IN CONTROLLING THE OUTPUT PRESSURE OF A TURBOCHARGER IN RESPONSE TO THE MANIFOLD PRESSURE WITH COMPENSATION FOR PRESSURE DROP AT THE THROTTLE CHARACTERIZED BY A REFERENCE UNIT DISPOSED IN THE HOUSING FOR THE MANIFOLD PRESSURE TO ACT ON AND AT LEAST ONE DIAPHRAGM EXTENDING ACROSS SAID HOUSING TO APPLY THE PRESSURE DIFFERENTIAL BETWEEN THE MANIFOLD PRESSURE AND THE OUTPUT PRESSURE OF THE TURBOCHARGER. IN ONE EMBODIMENT, THE REFERENCE UNIT INCLUDES A BELLOWS OF A PREDETERMINED VOLUME UNIT IN RESPONSE TO THE TEMPLACEMENT OF THE REFERENCE UNIT IN RESPONSE TO THE TEMPERATURES FO THE GASES OF THE MANIFOLD. ANOTHER EMBODIMENT INCLUDING AN ADDITIONAL DIAPHRAGM AND VALVE MEANS FOR APPLYING ADDITIONAL PRESSURE TO THE REFERENCE MEANS TO COMPENSATE FOR THE ALTITUDE FOR THE SYSTEM TO PREVENT OVERSPEEDING OF THE TURBOCHARGER.

1971 M. w. MUELLER TURBOCHARGER CONTROL Filed Nov. 6, 1969 3sheetsfiheet l lNvliN'lUk.

Mao v MMELLGR Get. 12, 1971 M. w. MUELLER TURBOCHARGER CONTROL FiledNov. 6, 1969 3 Sheets-Sheek. 2

Mm 70/V W/ Maui? (um/wax 1971 M. W. MUELLER TURBOCHARGER CONTROL FiledNov. 6, 1969 3 Sheets-Sheet 3 3,611,711 TURBOCHARGER CONTROL Milton W.Mueller, Cleveland, Ohio, assignor to TRW lino, Cleveland, Ohio FiledNov. 6, 1969, Ser. No. 874,496 lint. Cl. FtlZb 37/00 US. CI. 60-13 11Claims ABSTRACT OF THE DISCLOSURE A control unit which is particularlyuseful in controlling the output pressure of a turbocharger in responseto the manifold pressure with compensation for pressure drop at thethrottle characterized by a reference unit disposed in the housing forthe manifold pressure to act on and at least one diaphragm extendingacross said housing to apply the pressure differential between themanifold pressure and the output pressure of the turbocharger. In oneembodiment, the reference unit includes a bellows of a predeterminedVOlume of gas which schedules the displacement of the reference unit inresponse to the temperatures of the gases of the manifold. Anotherembodiment includes an additional diaphragm and valve means for applyingadditional pressures to the reference means to compensate for thealtitude for the system to prevent overspeeding of the turbocharger.

BACKGROUND OF THE INVENTION Field of the invention The present inventionis directed to a control unit responsive to a fluid pressure and inparticular a control unit and method of controlling for a turbochargersystem.

Prior art In the fluid handling art and in particularly in systems suchas a turbocharger system which supplies air at a pressure for an enginesuch as an airplane engine, the output of the turbocharger must becontrolled in response to the required manifold pressure and preferablymust be adjusted for the altitude of the aircraft and for the density ofthe gases being provided by the turbocharger. Present systems accomplishthis by the pilot or airplane personnel manually making adjustments inresponse to indication sensed from various points in the turbochargersystem to control the speed of the turbocharger. Automatic controlsystems have been proposed which include a series of sensing unitsmeasuring pressure at various points in the system against theirrespective reference unit with the output of each of the sensing unitsbeing interconnected to provide an ultimate summation of their signal tothe control circuit. Such systems require extensive mechanical linkagesbetween the various sensing units and extensive adjustments of thevarious reference units to obtain the desired control for theturbocharger systems.

SUMMARY OF THE INVENTION The present invention overcomes thedifliculties of prior proposed methods of controlling the speed ofturbocharger by providing a single unit capable of the sensing pressuresin a line in more than one place and provides a single output signal foruse in controlling the source of power for the turbocharger. Oneembodiment includes means which makes adjustments for the altitude ofthe aircraft to prevent the turbocharger from being damaged by excessivespeeds. In another embodiment, temperature sensing means are included inthe unit to adjust the single output in response to the temperature ofthe fluids being measured.

Accordingly, it is an object of the present invention to provide amethod of controlling and a simplified control $1,611,111 Patented Oct.12, 11971 unit providing a single output signal in response to pressureconditions taken from two points of a fluid passageway.

Another object of the present invention is to provide a method ofcontrolling and a control unit providing a single output signal inresponse to measurements of pressures from two points in a system withthe signal being adjusted for changes of temperature of the system.

A still further object of the present invention is to provide a methodof controlling and a control unit capable of providing a control signalin response to the pressures from various points in a control systemwith compensation for the altitude of the aircraft using the system.

Other objects, features and advantages of the invention will be readiyapparent from the following description of the preferred embodimentsthereof taken in conjunction with the accompanying drawings althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concept of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic illustrationof a turbocharger control system utilizing a control device and methodof the present invention;

FIG. 2 is a longitudinal cross-section with parts in elevation of thecontrol device used in the present invention;

FIG. 3 is a partial cross-section with parts in elevation similar toFIG. 2 of an embodiment of the control device of the present invention;and

FIG. 4 is a partial cross-section with parts in elevation of anotherembodiment of a control device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although the principles of thepresent invention are of utility in a control unit used in applicationwhere the pressures taken from at least two points of a fluid passagewayare necessary for the proper control of the fluid therein, theprinciples are particularly useful when incorporated in a control unitfor a turbocharger system which is diagrammatically illustrated in FIG.1 and generally indicated at 10.

A turbocharger system 11) comprises a turbocharger 11 having a rotor 12,an intake 12 and an output 13 which supplies input pressure of air to athrottle 14! and as illustrated supplies air through a restriction 15 toa conduit leading to the cabin of an aircraft. The air passing throughthe throttle 14 enters a manifold 16 of an engine 17. To drive theturbochrager 11, a drive source or power supply is supplied by conduit18 to the turbocharger 11. As i1- lustrated, the supply 18 is connectedto the exhaust 19 of the engine 17. To vary the amount of the supply, avalve means such as a wastegate 20 which is illustrated to be abutterfly valve can be opened to bypass a portion of the exhaust in thepipe 19 out an exhaust bypass pipe 21. To actuate the butterfly valvemeans .20, a hydraulic actuator 22 connected to a control means 23 byconduits 24, 25 and an oil supply 26.

The hydraulic actuator 22 comprises a single acting piston 27 actingagainst a spring 28 and having a rod 29 connected to the valve member 30of the valve means 21 Fluid acting on the piston 27 forces the valvemember 31) to a closed position. By controlling the amount of fluid bledfrom the piston chamber through the conduit 24, the control unit 23 canadjust the position of the piston 27 resulting in positioning the valvemember 30 in any desired position to allow any amount of bypassing ofthe gases of the engine exhaust line 19 and then reduce the exhaustgases driving the rotor 12 of the turbocharger 11.

The pressure in the output 13 of the turbocharger 11 is dependent uponthe speed of the rotor 12 of the turbo charger and on the pressure ofthe intake 12 of the turbo charger. Since the intake pressure 12' is notalways constant for example in aircraft applications it varies with thealtitude and the speed of the aircraft, the only effective means ofvarying or controlling the output pressure in the passageway 13 is bycontrolling the speed of the rotor 12 of the turbocharger 11. If theinput pressure were constant, a decrease in the speed of the rotor 12will decrease the pressure in the output passageway 13 and an increasein rotor speed will increase the output pressure. If a constant outputpressure is desired, the speed of the rotor 12 must be varied tocompensate for variations in the head of the intake 12 of the turbine.

Since the operation of the engine 17 is dependent upon the manifoldpressure 16, the supply of fluid to the manifold must be controlled tomaintain the pressure in the manifold 16 at the desired level. Asillustrated in FIG. 1, the control unit 23 has a pressure responsivereference means generally indicated at 31. If the pressure in the outputpassageway 13 were directly applied by a conduit 32 to the referencemeans 31, the pressure in the output 13 of the turbocharger would besensed. However, the control unit 23 would not compensate for changes inthe demands in the manifold pressure 16 in response to the settings ofthe throttle 14. One disadvantage with such a systern would be theapplying of a tremendous pressure on the throttle 14 which is notrequired.

Another possibility would be to sense the pressure of the manifold 16 byuse of a conduit such as 33 which would directly apply the pressureagainst the reference means 31. Such a system would be ideal if thethrottle 14 were completely open so that there would be no pressure dropor substantially little pressure drop thereacross. However, when thereis a substantial pressure drop and when the reference means 31 is set toopen the control circuit at a predetermined pressure, the turbocharger11 is trying to create the desired pressure. By trying to increase thepressure in the manifold 16, the turbocharger 11 causes an undesirableback pressure on the engine 17 through the exhaust line 19. To overcomethis disadvantage, the first embodiment of the present invention whichis best illustrated in FIG. 2 provides a control unit generallyindicated at 34.

The control unit or device 34 comprises a housing made up of housingportion 35, an annular ring 36, and a cuplike portion 37 which are heldtogether by fastening means such as the screws 38 with appropriate sealsbeing provided. The housing portion has a cavity 39 with an inlet port40 and an outlet port 41. The cavity 39, which is formed by a boreextending through the housing portion 35 has internal threads 42 at oneend of the bore to threadedly receive an end cap 43, which closes oneend of the bore to form the cavity. The bore forming the cavity 39 atthe opposite end to the threads 42 is provided with a counterbore 44 andadjacent to the counterbore 44 with an annular groove 45 receiving asnap ring or retainer 46.

A valve assembly 47 is disposed in the cavity 39 and comprises a valvebody 48, which is biased towards an end surface 49 of the cap 43 by aspring 50 acting between a surface 51 of the valve body 48 and a plate52 which rests on a sealing plate 53 retained in the cavity 39 by thesnap ring 46. The sealing plate 53 has appropriate sealing means toprovide a fluid tight closure of the cavity 39 adjacent the snap ring46.

The valve body 48 has an axial passageway 55 which is in communicationwith a radially extending passageway 56. Key means 57, comprising a pinand groove acting between the wall of the cavity 39 and the valve body48, maintains the passageway 56 in alignment with the inlet port 40. Thepassageway 55 terminates with the lower surface 51 to form a valve seatfor a valve member 58 which is carried on the valve shaft or stem 59which extends out of the cavity through axial openings in the plates 52and 53.

In order to minimize the etfect of the fluid passing through the valveassembly 47, the valve stem 59 supports a piston 60 which is slidablyreceived in the bore 55 and is axially spaced from the valve member 58.Thus fluid entering the bore 55 applies an upward force on the piston 60which counteracts the force tending to force the valve member 58 awayfrom the valve seat.

The cap 43 contains an adjustment means generally indicated at 61 whichsupplies an adjusting force by varying the spring pressure of a spring62 acting on the pistons 60. The spring 62 biases the valve member 58toward an open position. Each of the parts of the adjustment means 61includes appropriate seals and a lock nut means to hold the adjustmentunit 61 in the desired position. The valve assembly 47 is effectively aservo valve means or assembly which responds to movement of the valvestem 59 to control the flow of fluid through the inlet port 40 to theoutlet port 41.

Referring to FIG. 1, the position of the valve member 58 will controlthe flow of fluid in the lines 24 back to the oil supply or thereservoir of the oil supply 26. Since the oil supply to the actuator 22is supplied at a constant pressure, the bleeding off through the line orexhaust 24 will enable the piston 27 to assume a predeterminedequilibrium position in the cylinder with the pressure acting on thepiston balanced by the force of spring 28. By increasing the amount offlow through line or conduit 24, the spring 28 will force the pistontowards the ports which causes the valve member 30 of the wastegatevalve to move toward an open position. By reducing the flow through thevalve assembly 47 by moving the valve member 58 against its seat, thepressure acting on the piston will increase and cause it to be movedagainst the spring 28 to force the valve member 30 towards the closedposition.

The control unit 34 as illustrated in FIG. 2, includes a pressuresensing device which ultimately controls the position of the valvemember 58 to control the amount of fluid passing through the servo valveassembly 47. To provide chambers for the various fluid pressures to acton the sensing means, the housing portion 37 has a cavity '65 in which apressure responsive reference means indicated at 66 is disposed. Thereference means 66, which is similar to reference 31, includes a bellows67, a bellows plate 68 attached to the bellows and a bellows spring 69acting on the plate 68 to bias the bellows to an extended position.Reference means 66 which is mounted in the cavity 65 in a fixed positionby suitable means such as a bolt or screw arrangement 70, also includesa spring base plate or ring 71 which can be of different sizes or can beshimmed to change the spring force of the spring 69.

An extension of the valve stem 58 which extends through the bores or theopenings of the plates 52 and 53 is connected to a portion of thebellows plate 68 and acts as a linkage to transfer movement of thereference means 66 to the valve member 58.

As mentioned above, it is desirable to apply the pres sure of themanifold against the reference means 66 and to apply the pressuredifferential between the manifold pressure and the output pressure ofthe turbocharger against the reference means. This is accomplished byproviding a diaphragm 72 which is rigidly connected to the shaft or stem59 or as illustrated is rigidly attached by an expanded rivet means 73to a portion of the bellows plate 68. The diaphragm 72 seals the cavity65 to form a first pressure chamber and coacts with the counterbore 44of the portion 35 to form a second pressure chamber 74. Suitable portmeans are provided in the body portions for supplying a fluid pressureto each of the fluid pressure chambers 74 and 65.

In operation, the displacement of the reference means 66 positions thevalve member 58 via the linkage of the stem 59 with respect to the valveseat of the servo valve assembly 47. The reference means 66 is displacedwhen the force developed by the fluid pressure exceeds a predeterminedforce value or set point which is dependent on the spring force of thebellow spring 69 minus the spring force of the spring 62 of theadjustment means. If both of the pressures in the chambers 65 and 74 areequal which would occur when the pressure drop across the throttle 14 isnegligible, the force acting on the reference means 66 would be thepressure in the chamber 65 times the area that it is acting on which isthe bellows area. When the pressure or force developed by the pressurein the cham ber 65 exceeds the predetermined value or set point, thereference means 66 will be displaced and move the valve member 58 fromits seat. The amount of displacement of the reference means 66 andtherefore the valve member 58 will be proportional to the forcedeveloped by the pressure in the chamber 65 exceeding the predeterminedvalue.

Since the throttle 14 may be in the setting which causes a pressure dropthereacross, the pressure acting in the chamber 74- which is thepressure at the output 13 of the turbocharger 11 is greater than themanifold pressure 16 which is applied to the chamber 65. The result isthat the diaphragm 72 will be flexed by the pressure differential of thetwo pressures acting on its sides, and the pressure differential will beapplied against the reference means 66 along with the pressure in thechamber 65 being ap plied thereto. The force developed by the pressuredifferential applied to the diaphragm is dependent upon the area of thediaphragm which is larger than the bellows area and the amount of thepressure drop across the throttle 14. The application of the sum of theforces caused by the pressure differential and the pressure acting onthe bellows cause displacement of the reference means at a lowermanifold pressure and reduces the speed of the rotor 12 of theturbocharger 11.

Since the area of diaphragm 72 is larger than the bellows area, the sumof the forces acting on the reference means is greater than if theoutput pressure of passage 13 were directly applied to the bellows 67.Therefore, the control device 34 has effectively adjusted the set pointfor the reference means 66 in response to the change in the pressuredrop across the throttle 14. Thus, the control device 34 isautomatically scheduled for variation in the throttle setting, whichscheduling is desirable.

As mentioned above, with the displacement of the reference means 66, thevalve member 58 is moved off of the valve seat to allow fluid flowthrough the servo control 47 which flow varies the pressure applied tothe piston 27 to cause it to assume a new position in its cylinder withthe result of positioning the valve member 30 of the Wastegate valve toa new position causing a change in the exhaust pressures applied to theturbocharger 11. To prevent the hunting or overcorrection for thechanges in the sum of the forces created by the pressures,characteristic lags can be engineered into the control system whichtends to smooth the operation to prevent overcorrecting of the controlcircuit for a pressure change. Such lags are a question of design whichare within the ordinary skill of the design engineer.

In the discussion, the bellows 67 was considered to be an evacuatedmember with only a dampening fluid applied therein. Thus the heating ortemperature of the bellows 67 does not substantially effect the amountof force necessary to cause displacement of the reference means 66. Incertain applications such as an aircraft, the density of the fluid orgases being supplied to the manifold 14 is a critical requirement. Forexample, during a very hot day on a hot runway, the output of theturbocharger 11 can be at a maximum; however, the density of the gasesdue to their temperature is such that maximum power production for theengine 17 is not occurring. To compensate for the density of the fluidssuch as the gases being provided by the turbocharger, it is desirable toprovide means in the control system which will compensate for thedensity of the gases.

Since the density of the air is related to its temperature, a provisionof a bellows 67 charged with a predetermined volume of gas at apredetermined pressure and temperature can be utilized. By providing thebellows 67 which has this predetermined mass of gas, the bellows issensitive to the temperature of the air in the chamber 65.

For example, with a high temperature in the air in chamber 65, thepressure in the bellows due to the increase of temperature will increaseand effectively vary the predetermined value or set point in response tochanges in the temperature. With the bellows filled with the gas chargeat a known temperature and pressure, the reference means 66 will includemeans sensitive to the temperature, which means will adjust thepredetermined value for displacement in responsee to increases anddecreases of the temperature. Thus, when the aircraft using such asystem is operating in a hot ambient temperature, the control systemwill compensate for the loss of density in the gases by providing ahigher pressure than a system which does not have the temperaturesensitive means.

The control unit 34 provides a single error signal for the servo valveunit 47 by considering the pressure in the manifold 16, the outputpressure of the turbocharger 11, and the density of the gases beingsupplied by the turbocharger. However, in an aircraft application athigh altitudes, the lower density of the air due to the altituderequires higher speed for the turbocharger to maintain the predeterminedpressures. Such speed can have the detrimental effect upon theturbocharger 11 in an attempt of the turbochargers rotor 12 toeffectively run away. A second problem is due to the rarification of theair at a high altitude resulting in a reduction of cooling of the unitscausing the engine to overheat. In order to compensate for theseproblems, means must be provided to prevent the rotor 12 from exceedinga maximum speed. To prevent the speed of the rotor from exceeding acertain limit, the control device should include means to schedule thedevice for the altitude of operation by reducing the set point of thereference means 66. A control unit generally indicated at in FIG. 3 isan embodiment of the control unit provided with means to compensate foraltitude changes.

The control unit 80 having a servo valve assembly 47 which is the sameas that of the previously described embodiment of FIG. 2, has anadditional annular body portion or ring 81 disposed between the annularring 36 and the body portion 35. The diaphragm 72 is disposed betweenthe annular rings 81 and 36 and a second diaphragm 82, which is operablycoupled to stem 59, is disposed between annular rings 81 and housingportion 35. With the positioning of the diaphragms 72 and 82, threepressure chambers 65, 83 and 84 are formed. As in the previouslydescribed embodiment the pressure chamber 65 is substantially the sameand is formed by the cavity 65 and the diaphragm 72. The pressurechambers 84 and 83 are in communication with each other by a restrictedorifice 85 in the diaphragm 82 which orifice enables the pressure ofchamber 84 to leak into chamber 83. Ports (not illustrated) are providedfor applying a fluid under pressure to the chambers 65 and 84 while thechamber 83 has a port 87 in the annular .ring 81 which port terminatesin a check or relief valve means generally indicated at 88. The orifice85 balances the pressure acting on diaphragm 82 except when there isflow through the orifice due to the opening of relief valve 88.

The check valve means 88 includes a housing portion 89 having a chamber90 which contains a resilient means such as a spring 91 and a stemsupport means 92. A valve member 93 rests on a seat 94 and is normallybiased to the closed position by the spring 91 and atmospheric pressureacting on the valve member 93. The relief valve means 88 opens to ventthe chamber 83 as the pressure therein applies a force to the valvemember 93 which exceeds the force of the spring 91 and the atmosphericpressure on the valve member 93.. Thus, the chamber 83 is vented at aset point where the pressure differential between the pressure in thechamber and atmospheric pressure exceeds the spring force. By selectionof the characteristic of the spring 91, the valve means 88 will open ata predetermined atmospheric pressure or altitude. If the valve means 88were not provided, the unit would schedule the set point downward for anincreased altitude starting at sea level.

In operation, at low altitudes the manifold pressure is applied via theports to the chamber 65 to act on the reference means 66, the outputpressure of the turbocharger 11 is applied via ports to the chamber 84to act on the diaphragm 82. Assuming a constant pressure setup, pressurein the chamber 83 will be substantially similar to that in chamber 84 sothat the diaphragm 72 will respond as the diaphragm 72 in the previouslyexplained embodiment to apply the pressure differential between themanifold pressure and the output pressure to the pressure responsivemeans 66. One advantage of the two-diaphragm setup is that the orifice85 and the diaphragm 82 offers a resistance to any quick or substantialpressure changes in the output pressure of the turbocharger 11 causing alag which smooths out the control function and is desirable.

When the airplane utilizing the system reaches a predetermined altitude,the pressure in the chamber 83 exceeds the force of the spring 91 andthe atmospheric force acting on the valve member 93 causing the reliefvalve means 88 to open to vent the chamber 83. At that time, thepressure differential acting on the diaphragm 72 will equal thedifferential between the pressure in chamber 65 and the pressure in thechamber 83 which will be equal to that pressure necessary to open therelief valve 88. Since the chamber 83 has been vented, there will be apressure differential between the pressure chamber 83 and the chamber 84acting on the diaphragm 82.

As illustrated, the diaphragm '82 is of a larger diameter than thediaphragm 72 so that it will apply an additional force greater than theforce applied by the diaphragm 72 to the reference means 66 to causedisplacement of the reference means. As the altitude continues toincrease, the pressure in the chamber 83 necessary to cause the reliefvalve to vent the chamber to the atmosphere will decrease so that thepressure in the chamber 83 will be the atmospheric pressure plus thespring pressure created by the spring 91. The net result is that theforce caused by the pressure in the chamber 84 acting on the diaphragm82 will increase as the altitude of the airplane increases to cause anincrease in the additional force applied to the reference means 66 andtherefore, the unit 80 is scheduled for an altitude above apredetermined altitude. The amount of reduction in the set point toreduce the speed of the rotor 12 is dependent on the ratio between thearea of the diaphragm 82 and 72. Since the ratio must be larger toprovide proper control at higher altitudes practical limitation on thesize of diaphragm 82 limits the maximum altitude for which the unit 80provides the proper control function.

In order to provide a control system which provides a proper controlcharacteristic for the turbocharger at greater altitudes than that ofthe embodiment illustrated in FIG. 3, another embodiment generallyindicated at 100 (FIG. 4) incorporating the servo control valve means 47is provided. As in the peviously described embodiments, the controlmeans or unit 100 has a housing made up of housing portions 35, ring 36and housing portion 37 and utilizes the diaphragm 72. Additional housingportions 101 and 102 are placed between the annular ring portion 36 andthe portions 35, and a diaphragm 103 which has a restricted orifice 104and is coupled to stem 59, is disposed betweenthe body portions 101 and102.

Body portion 101 has a bore which coacts with a diaphragm 103 to form achamber 105. The body portion 102 has a cavity which coacts with thediaphragm 103 to form a chamber 106 which is vented by a passageway 107to the atmosphere. The housing portion 35 is provided with an inlet port108 for receiving the gas from the outlet passageway 13 of theturbocharger 11. Portions 101 and 102 respectively are provided withpassageways 109 and 1.10 respectively for conducting the pressure fromthe port 108 to a chamber 111 acting on one side of the diaphragm 8 72.Thus the diaphragm 72 functions as it functioned in the embodiment ofFIG. 2.

The body portion 101 supports a valve means 113 including a valve member114 cooperating with a valve seat 115. The valve means 113 provides acontrolled communication between the passageway 109 and the chamber 105and the valve means is actuated by the valve member 113 being connectedto an actuating means including a bellows means 116 mounted on theoutside of the ring portion 101.

The bellows means 116 senses the atmospheric pressures and at apredetermined atmospheric pressure begin to lift the valve member 114from the valve seat 115. With the movement of valve member 114 from thevalve seat 115, pressure in the passageway 109 enters the chamber 105 toact on one surface of the diaphragm 103 to add an additional forceacting on the reference means 66 to cause the valve member 58 to belifted from its seat in the servo valve means 47. Since the chamber 106is vented to the atmosphere, the pressure in the chamber 105 issubstantially unopposed and even a small diaphragm 103 can exert thenecessary additional pressure to the reference means 66 to compensatefor the increased altitude.

The valve member 114 is contoured with respect to the seat 115 so thatas the displacement from the seat 115 increases the size of the openingincreases. With the increase of the size of the opening of the valvemeans 113, more fluid bleeds into the chamber 105 to increase thepressure therein. Thus, as the altitude increases above thepredetermined altitude, the pressure in the chamber 105 increases toincrease the pressure differential acting on diaphragm 103 to increasethe additional force being applied to the reference means 66. Since thepressure in the chamber 105 will increase with the increasing of thealtitude due to the increased movement of the valve member 114 by thesensing means 116, the control unit will provide the proper controlfunction to prevent overspeedin-g of the rotor 12 of the turbocharger 11for the ambient atmospheric conditions.

The bellows means 116 as illustrated includes a sealed evacuated doublebellows which expands as the atmospheric pressure decreases. Otherproper preloaded bellows arrangements which function in equivalentmanner can be readily utilized.

In operation below the predetermined altitude, the valve means 113 isclosed and the pressure in chambers 1.05 and 106 are substantiallyequal. Thus the control unit 100 will function in a manner similar tothe unit 34. As the altitude set point is reached, the bellows means 116moves the valve member 114 from the seat 115 to open the valve means 113to enable fluid pressure in passage 109 to bleed into the chamber 105.Even though a portion of the fluid will bleed through the orifice 104, apressure differential will be applied to the diaphragm 103 to exert theadditional force on the reference means 66 to compensate for theatmospheric conditions. As the altitude increases the valve means 113 isopened further to increase the amount of fluid bled into chamber toincrease the pressure therein and increase the pressure differential onthe diaphragm 103. Thus the reduction in the set point increases with anincrease in the altitude.

Assuming operation above the predetermined altitude by an aircraft usingthe control unit 100, the pressure in the chamber 105 has applied aforce acting on the reference means 66. With a decrease in the altitude,the valve means 113 reduces the amount of fluid flowing into the chamber105; however, the orifice 104 will continue to bleed pressure from thechamber 105 to cause the pressure therein to be reduced. As the altitudeis decreased below the predetermined level or point, the valve means 113is closed and the chamber 105 will lose its pressure through the orifice104 until the pressure acting on the diaphragm 103 is balanced.

The control unit 100 provides the proper control function to maintainthe desired control of the turbocharger 11. Due to the arrangement ofthe pressure chamber and diaphragm, the control unit 100 can provideproper con trol function for higher altitudes than the control unit 80which has a practical altitude limit due to the ratio of the size of itsdiaphragms.

The reference means 66 utilizes either an evacuated bellows which wouldnot be responsive to temperature changes in the fluid or gases in thechamber 65 or it can utilize a gas charged bellows which is temperatureresponsive. By using a temperature responsive bellows in the referencemeans 66, the control units 80 and 100 can inelude a scheduling functionfor the density of the gases in the manifold 16.

As illustrated in FIG. 1, the output of the turbocharger '11 alsoprovides pressure for the cabin of the aircraft. Thus it is essentialthat the pressure in the output passageway 13 is not greater thannecessary at low throttle or part throttle operations since the excesspressure of the output of the turbocharger 11. would cause an unbearablecondition upon the occupants of the cabin. As illustrated, the outlet 15going to the cabin includes a restriction which helps reduce thepressure being applied to the cabin and by properly selecting the sizeof the restriction and the size of the conduit 32, the necessarypressure in the cabin will always be maintained without being adverselyaffected by the engine operation and the operation of the control unitsuch as 34.

Each embodiment of the control unit of the system prevents overspeedingof the rotor .12 of a turbocharger 11 and prevents the decompression ofthe cabin at part throttle operations or during changes in the throttlesetting. Each control unit also prevents inefiicient back pressure onthe engine exhaust at partially closed throttle setting. All of thecontrolling features are accomplished by a single unit using a singlereference and therefore eliminate the problems of the prior artcontrollers such as a system using multiple units which requiresmechanical linkages between the units.

I claim as my invention:

1. A control device for a system for controlling the output pressure ofa turbocharger in response to a manifold pressure of the engine beingsupplied by the turbocharger by varying the amount of the power sourceapplied to the turbocharger, said control device comprising a housinghaving a cavity; a pressure responsive reference means disposed in saidcavity, said reference means being displaceable at a predetermined valueof force applied thereagainst; means connected to said reference meansand extending out of said cavity to actuate a control means in responseto displacement of said reference means to control the amount of powersource to the turbocharger, diaphragm means operatively connected tosaid reference means and extending across said cavity to provide a pairof chambers, means applying manifold pressure of the manifold to one ofsaid chambers to act on said reference means and means applying theoutput pressure of the turbocharger to the second of said cavities,whereby said reference means is acted on by the manifold pressure and apressure differential between said manifold pressure and the outputpressure to create a proportional signal in response to the amount ofdisplacement of said reference means.

2. A control device according to claim 1 wherein said reference meansincludes a bellows means and a spring means, said bellows means beingfilled with a predetermined volume of gas at a predetermined temperatureand pressure, whereby said gas of said bellows means changes in pressurein response to changes in temperature of the fluid in said first chamberto adjust the predetermined value of said reference means in response tochanges in the temperature of the fluid in the manifold.

3. A control unit for controlling the output pressure of a turbochargerin response to a manifold pressure of an engine supplied by saidturbocharger by controlling the power source to drive the turbocharger,said unit comprising a housing having a first and second cavities, saidfirst cavity having a fluid inlet and an outlet extending incommunication therewith, a fluid valve assembly disposed in said firstcavity; a reference means displaceable in response to a predeterminedvalue of pressure applied thereagainst disposed in said second cavity,means interconnecting said reference means and the valve member of said=valve assembly, a diaphragm means disposed across said second cavityand coupled to said reference means, said diaphragm means dividing saidsecond cavity into a first and second chamber, means for applying fluidpressure from said manifold to said first chamber to act directly onsaid reference means and on one side of said diaphragm means, and meansto apply the output pressure of said turbocharger to said second chamberto act on the other side of said diaphragm whereby said reference meansis displaced when said manifold pressure and the differential betweenthe output pressure and manifold pressure exceeds a predetermined.amount and said displacement is corresponding to the amount of excesswhich positions the valve member a distance corresponding to the amountof excess to vary the amount of control fluid passing through said firstcavity to vary the drive source to the turbocharger.

4. A control unit according to claim 3 which includes a second diaphragmdisposed in said second chamber to form a third chamber between saiddiaphrgams, said second diaphragm having an orifice to enable bleedingof fluid between the second and third chambers, said housing havingvalve means venting said third chamber when the pressure differentialbetween the third chamber and the outside of said housing exceeds apredetermined amount so that below the predetermined amount for thepressure differential, said diaphragms act to provide a pressuredifferential between said manifold pressure and said output pressure ofsaid turbocharger and at said predetermined amount, said seconddiaphragm applies additional force to said reference means to causedisplacement of said valve member at a lower predetermined value for thesum of the manifold pressure and the differential between the manifoldand output pressure.

5. -In a control unit according to claim 3' which includes a thirdcavity in said housing said third cavity being in free communicationwith the outside of said housing and having a diaphragm extendingthereacross to form a third chamber, said diaphragm having a bleedorifice therethrough to vent the third chamber formed in said thirdcavity to the outside, pressure responsive valve means interconnectingthe means for applying the output pressure to said second chamber andthe third chamber, said pressure responsive valve means including anactuating unit responsive to the atmospheric pressure, said pressureresponsive valve means being opened to interconnect the output pressureof said turbocharger to said third chamber to act on said diaphragm at apredetermined atmospheric pressure so that an additional force isapplied to said reference means to cause the displacement thereof at alower sum of the pressures in the manifold and output of theturbocharger to cause the valve assembly to reduce the power source tothe turbocharger to prevent o'verspeeding thereof.

6. In a control unit in accordance with claim 3 wherein said referencemeans includes a bellows containing a predetermined amount of gas at apredetermined tempera ture, volume and pressure, said bellows beingdisposed in said second cavity to be heated to the temperature of thefluid in the first chamber, so that the pressure of the gas in thebellows is proportional to the temperature of the manifold fluid in thefirst chamber to increase and decrease the predetermined vaue of saidreference means in response to increases and decreases of thetemperature thereof.

7. A device for controlling the output pressure of a turbocharger inresponse to a manifold pressure of an engine being supplied by theturbocharger by varying the amount of the power source applied to theturbocharger, said device including a pressure responsive meansproviding a reference of a predetermined value and having a portiondisplaceable when a pressure of a predetermined value is appliedthereto, control means regulating the amount of power source applied tosaid turbocharger, linkage means interconnecting said pressureresponsive means and said control means; means for applying fluidpressure of the manifold against said pressure responsive means andmeans simultaneously applying the pressure differential between theoutput pressure of the turbocharger and the manifold pressure againstsaid pressure responsive means so that the control means receives aproportional signal from the pressure responsive unit when the sum ofthe manifold pressure and the pressure differential exceeds apredetermined amount with said signal being proportional to the amountof excess.

8. In a method of controlling the output pressure of a turbocharger inresponse to the manifold pressure of an engine associated with theturbocharger by controlling the power source for the turbocharger, theimprovement comprising the steps of simultaneously applying the manifoldpressure and a pressure differential between the output pressure and themanifold pressure against a pres sure sensitive reference means,generating an error signal as a sum of the manifold pressure andpressure differential exceeds a predetermined value of said referencemeans, said error signal being proportional to the excess of the sumover the predetermined value, utiliz ing the error signal to vary theamount of the power source supplied to the turbocharger so that thespeed of the turbocharger is varied in response to the error signal inan amount proportional to the amount of the error signal to vary theoutput pressure of the turbocharger.

9. In a method according to claim 8' which includes the step ofcompensating in the error signal for variation in the temperature of thegas in the manifold.

'10. In a method according to claim 8 which further includes the stepsof sensing the atmospheric pressure, and applying additional pressure tothe pressure responsive reference means as the atmospheric pressuredrops below a predetermined value, said additional pressure beingapplied along with the sum of the manifold pressure and the pressuredifferential, whereby an error signal for reducing the speed of theturbocharger is produced for a lower value of the sum of the manifoldpressure and pressure differential and prevents overspeeding of theturbocharger as the atmospheric pressure is decreased below apredetermined value.

11. A device for generating a signal in response to a pressure of afluid taken from at least two different points of a fluid passagewayextending from a turbocharger to an intake manifold of an engine,comprising reference means displaceable in response to a force appliedthereto; means for applying a fluid pressure from the engine manifold tosaid reference means to create a first force acting thereon; means forattaining a pressure differential between the fluid pressure taken fromsaid engine manifold and a second point taken at an output of theturbocharger and applying said pressure differential to said referencemeans to create a differential force acting on said reference meanssimultaneously with said first force; and means coupled to saidreference means for transmitting the amount of displacement of thereference means is proportional to the sum of the first force anddifferential force to a control system for controlling a power source ofthe turbocharger so that as the sum of first force and differentialforce increases, the power source to the turbocharger is decreased tocause a corresponding decrease in the output of the turbocharger.

References Cited UNITED STATES PATENTS 2,567,486 9/1957 Johansson 132,878,797 3/1959 Madden 6013 X 2,896,598 6/1966 Reggio 123-119 CE3,035,408 5/1962 Silver 6013 3,096,614 7/1963 Silver et al. 60133,104,520 9/1963 CaZier et a1. 6013 3,195,805 7/1965 Cholvin et a1. 6013X 3,257,796 6/1966 Updike 6013 3,386,427 6/1968 Powell et al. l23119 CE3,389,553 6/1968 Hardy et a1. 60-13 3,421,314 1/1969 Michalke 6013 AL L.SMITH, Primary Examiner US. Cl. X.R.

